1. Field of the Invention
The present invention relates to a heating crucible that has a uniform deposition rate and good deposition reproducibility. The present invention also relates to a deposition apparatus that uses the heating crucible in a deposition process.
2. Description of the Related Art
Electroluminescence display devices are expected to be the next generation of emissive display devices due to their wide viewing angles, high contrast and high response speed.
Electroluminescence display devices are classified as either organic light emitting display devices or inorganic light emitting display devices depending on the material that forms an emission layer (EML) included therein. Organic light emitting display devices are brighter and have a higher driving voltage and higher response speed than inorganic light emitting display devices. Organic light emitting display devices can also display color images.
An organic light emitting diode (OLED) is an organic light emitting display device. An OLED includes an inner layer located between electrodes facing each other. The inner layer can be, but is not limited to, a Hole Injection Layer (HIL), a Hole Transport Layer (HTL), an EML, an Electron Transport Layer (ETL), an Electron Injection Layer (EIL). These layers are known as organic thin films.
Organic thin films such as the HIL, HTL, EML, ETL, EIL, or the like can be formed on a substrate using a deposition method in a deposition apparatus to fabricate the OLED. In a typical deposition method, the internal pressure of a chamber is reduced to between 10−6 to 10−7 torr. The chamber contains a heating crucible that faces a substrate. Organic material is injected into the heating crucible, and the organic material is evaporated or sublimated to deposit the organic material on the substrate.
Organic materials must have a uniform deposition rate and good reproducibility to be uniformly deposited on a substrate to make organic light emitting display devices capable of reproducing a uniform image on an entire screen. Heating crucibles made of ceramic do not have a uniform deposition rate and good reproducibility.